1. Field of the Invention
This invention generally relates to a developer conveyor device applicable in electrophotographic copying machines of the image transfer type. More specifically, it relates to a developer conveyor device for positively conveying the developer to a developer receptacle portion or a developing portion when the residual developer remaining on the surface of an electrophotographic photosensitive medium has been removed therefrom for reuse after an electrostatic latent image formed on the photosensitive medium has been dry -or wet-developed and transferred to a transfer medium.
2. Description of the Prior Art
Generally in electrophotographic copying machines, an electrostatic latent image may be formed on an electrophotographic photosensitive medium by an electrophotographic method as disclosed in U.S. Pat. No. 2,221,776 wherein the surface of a photosensitive medium comprising a photoconductive layer superposed on a conductive back-up member is uniformly charged and then subjected to application of image light to form an electrostatic latent image, or an electrophotographic method as disclosed in U.S. Pat. No. 3,438,706 wherein the surface of a photosensitive medium having a chargeable dielectric layer on a photoconductive layer is uniformly charged and then subjected to simultaneous application of image light and charge of the opposite polarity or AC corona discharge to form an electrostatic latent image in accordance with the light-and-dark pattern of the original image, whereafter, if required, the surface of the photosensitive medium may be subjected to an overall exposure to thereby form an electrostatic latent image of high contrast, or any one of other various electrophotographic methods. The latent image so formed may be visualized by means of dry or wet developer and the visualized image may be transferred to a transfer medium such as ordinary paper or the like, whereafter the transferred image may be fixed by heat or the like. The surface of the photosensitive medium may be cleaned by cleaning means for repetitive use. Thus, in the copying machines of the image transfer type, cleaning of the photosensitive medium to remove the residual developer therefrom is an essential requisite and the developer so removed is collected from the cleaning station to a predetermined portion of the machine by attraction or by mechanical conveyor means, whereafter the collected developer is discarded or treated. As a copying machine accelerates its copying speed, the amount of the developer collected in a container is increased and must be discarded before the collected amount reaches the maximum capacity of the container. This has been greatly inconvenient in use. In such cases, therefore, it would be positively considered to guide the removed developer into developing means for reuse.
Means for conveying such developer to the developer receptacle or the developing portion may be a belt conveyor system, but this would offer numerous disadvantages such as complication of the apparatus, unstability of the conveyance, etc. An alternative may be a system whereby a ball-like chain belt is moved around in a tube, but such system would fail to smoothly convey fine toner particles and in addition, the toner itself would be subjected to extraneous pressure which would cause coagulation between toner particles, which in turn would lead to the necessity for the toner to be re-dispersed within the developing means, thus resulting in reduced quality of the copy image. Moreover, the toner to be collected and conveyed is in the form of very fine particles which are so poor in fluidity that the conveyance of the toner to the developing portion for reuse would be very difficult with such system. Also, this system could not practically be used with liquid developer. Thus, there has theretofore been proposed no stable system.